A Numerical Comparison of 2D and 3D Unsteady Confined Impinging Air Jets and Associated Microelectronics Cooling Impact

Abstract

A numerical investigation to compare the flow and heat transfer characteristics of 2D and 3D single impinging slot jets was performed at various Reynolds numbers. The present study is a continuation of the authors’ earlier work [1], and identifies the main similarities and differences arising from the expansion to the third dimension. For comparison purposes, a single slot jet impinges on an adiabatic lower wall with a flush mounted heat source. Two Reynolds numbers have been selected, 300 and 600, such that the jets are steady at the lower Reynolds number flow for both 2D and 3D models and unsteady for the higher Reynolds number flow. Both simulations are in the laminar regime. The steady cases at a Reynolds number of 300 show that the 3D slot jet produces the same values as the 2D case. The flow produces a symmetrical, steady flow hydrodynamic pattern with the jet being deflected laterally by the wall. By further increasing the Reynolds number to 600, a complex and highly unsteady flow develops for both 2D and 3D simulations. The complex flow patterns reveal the vortex pairing effects observed before for the 2D flows, leading to the jet “buckling and sweeping” behavior. However, the 3D unsteady jet produces results that deviate from the 2D unsteady case due to 3D viscous effects that are more pronounced than for the steady flow. The relevant difference between the 3D spatial behavior versus the 2D planar behavior occurring for the unsteady flows are documented by comparing the Nusselt numbers on the target wall for the cases under evaluation. Plots of the velocity, vorticity and temperature fields for both 2D and 3D cases are provided together with detailed discussion of the results.